measurementof)directphoton)collec9ve)flow)) in)au+au√ snn ... · mesons)spectraare)assumed)by) m...
TRANSCRIPT
Sanshiro Mizuno for the PHENIX collabora9on University of Tsukuba, RIKEN
mail to : [email protected]
Measurement Of Direct Photon Collec9ve Flow In Au+Au √sNN=200GeV collisions
at RHIC-‐PHENIX experiment
2014/08/06 ATHIC2014 @ Osaka 2
What are direct photons ?
Direct photons: all photons except those origina9ng from hadron decays. l Good probe since they penetrate the QGP l Created during all stages of the collision
hard scaHering
(thermal?) radiaLon from QGP
(thermal?) radiaLon from HG
jet-‐photon conversion
Jet fragmentaLon
hadron decay
p T(GeV
/c)
Lme
3
Φ3
v3 comes from par9cipant posi9on fluctua9ons, viscosity dampens higher order terms. • Define iniLal geometry calculaLng model • Constrain η/s of QGP
Φ2
⌫n =< cos{n(�� �n)} >
dN
d(�� n)= N0[1 + 2
1X
n=1
vncos{n(�� �n)}]
Φn : Event Plane
Higher Order Azimuthal Anisotropy
4
The pT spectra from p+p data is fi^ed and extrapolated below 2 GeV/c.
The excess of pT spectra are fi^ed and effec9ve temperature is extracted. It is about 240 MeV. Photons are emi^ed from very hot medium at early 9me of collisions.
a(1 + p2T /b)c
Ae�pT /Teff
arXiv:1405.3940v1
Direct Photon pT spectra
P.R.L. 109, 122302(2012)
It is observed that posi9ve γdir. v2 in low pT and the magnitude of it is comparable to that of hadron v2. Photon is emi^ed at late 9me of collisions, when temperature is low.
Direct Photon EllipLc Flow (v2)
5
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It is a challenge for models to explain simultaneously the excess of direct photon yield and the large ellip9c flow (v2).
Yield enhancement Suggests early emission when temperature is high at or above 300MeV Large ellipLc flow (v2) Suggests late emission, when temperature is low, collec9ve mo9on is large
Integrated emission differen9al emission
Direct Photon Puzzle
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To resolve the puzzle and constrain photon produc9on mechanisms, more differen9al measurements are needed. • Higher order azimuthal anisotropy (v3) It could help understanding and constrain photon produc9on mechanism. In this talk, new results for v3 in several centrali9es are shown.
MoLvaLon
(GeV/c) Tp0 2 4
0
0.05
0.1
0.15
(GeV/c) Tp0 2 4
0
0.05
0.1
0.15
8
π0, γinc. vn measurement γdec. vn esLmaLon from π0 vn Mesons spectra are assumed by mT scaling. Mesons vn are assumed by NCQ scaling. γdir. vn calculaLon Rγ measured by external photon conversion method is used.
⌫dir.n =R�⌫inc.n � ⌫dec.n
R� � 1R� = Ninc./Ndec.
Analysis Flow
π0
γinc.
v2 v3 0-‐60% centrality AuAu 200GeV E.P. : RxN(I+O)
arXiv:1405.3940
(GeV/c) T
p0 5 10 15-110
10
310
510
710
910
1110
(GeV/c) T
p0 5 10 15-410
-110
210
510
810
1110
(GeV/c) T
p0 5 10 15-410
-310
-210
-110
1
(GeV/c) T
p0 5 10 150
0.05
0.1
0.15
0.2
(GeV/c) T
p0 5 10 150
0.05
0.1
0.15
0.2
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Hadronic Decay Photon The pT spectra and vn are es9mated from π.
pT spectra : mT scaling vn : quark number scaling
π η ω
meson pT spectra γdec. pT spectra contribu9on ra9o (Ri)
meson v2 γdec. v2
ρ η’ all γdec.
vdec.n =X
i
Rivdec.in
p0
T
=q
p2T,⇡
0 +M2meson
�M2⇡
0
mT scaling decay photon vn
(GeV/c) Tp0 2 4
0
0.05
0.1
0.15
(GeV/c) Tp0 2 4
0
0.05
0.1
0.15
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Inclusive and decay photon vn comparison
γinc.
γdec.
⌫dir.n =R�⌫inc.n � ⌫dec.n
R� � 1
Direct photon vn are extracted from these devia9on via below func9on.
v2 v3 0-‐60% centrality AuAu 200GeV E.P. : RxN(I+O)
(GeV/c) T
p0 2 4
3v
0
0.05
0.1 0-60(%)3 v0π
3 vinc.γ
E.P.:RxN(I+O)Au+Au 200GeV
(GeV/c) T
p0 2 4
3v
0
0.05
0.13 vdir.γ
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The magnitude of γdir. v3 is similar to π0, a similar trend as a seen in case of v2. Photon azimuthal asymmetries may be affected by expansion of QGP.
The Result of Direct Photon v3
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(GeV/c) T
p0 2 4
3v
-0.1
0
0.1
0.23 vdir.γ
E.P. : RxN(I+O)
(GeV/c) Tp0 2 4
3v
-0.1
0
0.1
0.2 Au+Au200GeV
(GeV/c) T
p0 2 4
3v
-0.1
0
0.1
0.20-20(%) 20-40(%) 40-60(%)
η range of RxN(I+O) is from 1.0 to 2.8. Non-‐zero, posi9ve v3 is observed in all centrality bins. No strong centrality dependence: similar tendency as for charged hadrons (P.R.L. 107, 252301 (2011)) and π0.
Centrality dependence of Direct Photon v3
(GeV/c) T
p0 2 4
3v
-0.1
0
0.1
0.23 vdir.γ 3 v0π
E.P. : RxN(I+O)
(GeV/c) Tp0 2 4
3v
-0.1
0
0.1
0.2 Au+Au200GeV
(GeV/c) T
p0 2 4
3v
-0.1
0
0.1
0.20-20(%) 20-40(%) 40-60(%)
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The centrality (in)dependence of γdir. v3 is also observed for π0 v3.
γdir. and π0 v3 show similar trend
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0.0
0.1
0.2
0.3
v 2
gdirect (calorimeter)gdirect (conversions)
Au+AupsNN = 200GeV
RXP(I+O)
0 1 2 3 40.00
0.05
0.10
0.15
v 3
0-20%
0 1 2 3 4pT [GeV/c]
20-40%
0 1 2 3 4
40-60%
The calorimeter and conversion photon measurements are consistent within systema9c uncertainty.
Comparison of γdir. vn with the two methods
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π0 and γdir. v2 measurement by STAR
γdir. v2 in high ET region are consistent with 0 within systema9c uncertainty, while π0 has posi9ve v2.
Ahmed M. Hamed shown at QM
2014/08/06 ATHIC2014 @ Osaka 16
photon vn measurement by ALICE
v2
It is also observed that γdir. v2 is posi9ve in low pT at LHC-‐ALICE. v3 measurement is ongoing.
v3 γdec. v3 γinc. v3
arXiv:1212.3995v2 Friederike shown at QM
2014/08/06 ATHIC2014 @ Osaka 17
Soi photons are expected to do provide important keys to understand photon produc9on mechanisms and medium proper9es. Direct photon v3 are measured in several centrality bins. It is observed that
non-‐zero and posi9ve γdir. v3 the strength of γdir. v3 is comparable to hadron v3
They are similar trend to γdir. v2. don’t have strong centrality dependence
It is similar tendency to hadron v3. The other experiment also study direct photon vn measurement.
Summary
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Central Arm: Measure electrons and photons |η| < 0.35 Reac9on Plane Detector (RxN): Es9mate Event Plane Inner : 1.5 < |η| < 2.8 Outer : 1.0 < |η| < 1.5 MPC: Es9mate Event Plane 3.1 < |η| < 3.8 BBC: Es9mate Event Plane 3.1 < |η| < 3.9
Detector informaLon
2014/08/06 ATHIC2014 @ Osaka
MHBD: Real track Mvtx : Measured track
MHB
D[GeV
]
Mvtx[GeV] 20
Published Real photons in EMCal : 1 -‐ 20 GeV/c
large errors at low pT (resolu9on, contamina9on) Virtual photons from e+e-‐ : 1 -‐ 4 GeV/c New method Real photons are measured by e+e-‐ pair from external photon conversion at the HBD readout plane. ü less hadron contamina9on ü good momentum resolu9on pT range : 0.4 ~ 5GeV/c Extended to lower pT low staLsLcs
Photons by external conversion
1) real photon converts to e+e-‐ in HBD backplane 2) default assump9on: track come from the vertex 3) momentum of the conversion tracks will be mis-‐measured (see black tracks) 4) apparent pair-‐mass (about 12MeV) will be measured for phtons 5) assume the same tracks originate in the HBD backplane 6) re-‐calculate momentum and pair mass with this “alternate tracking model” 7) for true converted photons Matm will be around zero
Real track esLmated track
MHB
D[GeV
]
21 Mvtx[GeV] 2014/08/06 ATHIC2014 @ Osaka
External conversion photon
2014/08/06 ATHIC2014 @ Osaka 22
Ncoll-‐scaled pp fit external conversion pp virtual photon pp in EMCal(Run2003 data) pp in EMCal(Run2006 data) AuAu in EMCal(Run2004 data) AuAu from virtual photon(Run4 data) Using external photon conversion method achieved good agreement with previous results.
Au+Au
Min. Bias
Comparable measurement is achieved arXiv:1405.3940
2014/08/06 ATHIC2014 @ Osaka 23
γdir. vn with external conversion photon analysis charged π vn γinc. vn with external conversion photon analysis Rγ with external conversion photon analysis γdir. vn with Calorimeter π0 vn with Calorimeter γinc. vn with Calorimeter Rγ with external conversion photon analysis
The analysis informaLon
2014/08/06 ATHIC2014 @ Osaka 24
(GeV/c) T
p0 2 4
3v
0
0.05
0.1
0-60(%) (RxN(I+O))3 vdir.γ
Au+Au200GeV
(GeV/c) T
p0 2 4
3v
0
0.05
0.1
0-60(%) (RxN(In)+MPC)3 vdir.γ
Au+Au200GeV
RxN(I+O) : 1.0 <|η|< 2.8 RxN(In)+MPC : 1.5 <|η|< 3.8 The magnitude of v3 is comparable.
Comparison γdir. v3
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Inclusive photon vn is measured via conversion photon, and pT range is extended to low pT region.
(GeV/c) T
p0 1 2 3 4
2v
0
0.1
0.2 (RxN(I+O))2 vinc.γ
real photonexternal conversion photon
(GeV/c) T
p0 1 2 3 4
3v
0
0.1
0.2 (RxN(I+O))3 vinc.γ
real photonexternal conversion photon
(GeV/c) T
p0 1 2 3 42v
0
0.1
0.2Au+Au 200GeVAu+Au 200GeV
(GeV/c) T
p0 1 2 3 4
3v
0
0.1
0.2(GeV/c)
Tp0 1 2 3 4
2v
0
0.1
0.2
(GeV/c) T
p0 1 2 3 4
3v
0
0.1
0.2
0-20(%) 20-40(%) 40-60(%)0-20(%) 20-40(%) 40-60(%)
Comparison inclusive photon vn
26
π± and π0 pT spectra are fi^ed and its func9on is used for es9ma9ng the other meson pT spectra by mT scaling. They are used as a input.
p0
T
=q
p2T,⇡
0 +M2meson
�M2⇡
0
Input decay photon : pT spectra
27
The ra9o of Each meson pT spectra to π0 pT spectra is known to be constant at high pT.
Input decay photon : pT spectra
10�5
10�4
10�3
10�2
10�1
100
101
12p
p Td2 N
dpT
dy[(
GeV
/c)�
2 ]
0-20%
(a) Linnyk et al.vHees et al.Shen et al. (KLN)Shen et al. (MCGlb)direct g
20-40%
Au+AupsNN = 200GeV
(b)
0 1 2 3 4
10�5
10�4
10�3
10�2
10�1
100
101
40-60%
(c)
1 2 3 4 5pT [GeV/c]
60-92%
(d)
Linnyk et al.: PHSD transport model; Linnyk, Cassing, Bratkovskaya, P.R.C 89, 034908(2014) vHees et al.: Fireball model; van Hees, Gale, Rapp; P.R.C 84, 054906(2011) Shen et al.: Ohio hydro for two different ini9al condi9ons; Shen, Heinz, Paquet, Gale; P.R.C 84, 064903(2014) The yield itself is s9ll not perfectly described.
arXiv:1405.3940
2014/08/06 ATHIC2014 @ Osaka 28
Yield : data vs theories
2014/08/06 ATHIC2014 @ Osaka 29
0 1 2 3 40.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
v 2
gdirect (conversions)gdirect (calorimeter)
vHess et al. (b)vHess et al. (a)Linnyk et al.
0 1 2 3 4pT [GeV/c]
0 1 2 3 4
van Hees et al: P.R.C 84, 054906 (2011) Linnyk et al.: PHSD model, private communica9on
0-‐20% 20-‐40% 40-‐60%
Comparison γdir. v2 with theoreLcal calculaLons